The present invention relates to a work piece feeding machine, more precisely relates to a work piece feeding machine capable of feeding a work piece or work pieces together with a carrier.
Abrasive machines are widely used to polishing semiconductor wafers or lapping glass, crystal, etc. In the abrasive machine, work pieces, e.g., semiconductor wafers, are set in prescribed positions of the machine. The abraded work pieces are discharged from the abrasive machine. Setting and discharging the work pieces are executed by a work piece feeding machine. However, it is difficult to correctly position the work pieces in the abrasive machine.
Conventionally, the work pieces are chucked and set in through-holes of a carrier by a multi-joint robot (see Japanese Utility Model Gazette No. 3-29083). In this case, the work pieces are set in the carrier which has been previously set in the abrasive machine, or the carrier, in which the work pieces have been previously set, is set in the abrasive machine.
Further, positions of the work pieces are corrected when the work pieces are set. The correction is executed by the steps of: setting the work piece in a setting section of the abrasive machine; detecting positions of an outer edge of the work piece and an inner edge of the setting section; measuring a distance between both edges; and adjusting the distance so as to correct the position of the work piece in the setting section (see Japanese Patent Gazette No. 10-41372). In this case, a plurality of monitors are provided along the edges with regular angular separations, e.g., 120xc2x0, and the distances detected by the monitors are made equal by correcting the position of the work piece.
In the case of setting the carrier, in which the work pieces have been set, in the abrasive machine, the work pieces should be correctly set in the through-holes. If the carrier is made of a half-transparent material, difference of light intensity between the carrier and the through-holes is small, so it is difficult to stably detect the through-holes by optical means. To stably detect the through-holes, an expensive image processing unit is required, marks are provided to the carrier, and at least three cameras are provided for one work piece.
An object of the present invention is to provide a work piece feeding machine capable of correctly and efficiently setting a work piece in a through-hole of a carrier and feeding the carrier to a machine for a further step.
Another object is to provide an abrasive system capable of efficiently abrading a work piece.
To achieve the object, the present invention has following structures.
The work piece feeding machine of the present invention, which sets a work piece into a through-hole of a carrier and feeds the carrier holding the work piece to a machine for further treatment, comprises:
a loading unit for feeding the work piece to the through-hole of the carrier; and
a positioning unit detecting amount of displacement of the work piece with respect to the through-hole at a detecting position and correcting the position of the work piece in the through-hole on the basis of the detected amount of the displacement thereof,
wherein the positioning unit includes:
a lighting source section being provided on the work piece side or the carrier side, the lighting source section throwing polarized light on the work piece and the carrier at the detecting position;
a camera being provided on the carrier side or the work piece side, the camera receiving the polarized light from the lighting source section with selecting a polarizing direction so as to catch images of an outer edge of the work piece and an inner edge of the through-hole in a visual field thereof; and
an image processing section measuring the amount of displacement of the work piece with respect to the through-hole on the basis of positions of the outer edge of the work piece and the inner edge of the through-hole in the visual field.
In the work piece feeding machine, the work piece and the carrier are provided between the lighting source section and the camera, and the work piece and the through-hole of the carrier are detected by polarized light. Therefore, the amount of displacement of the work piece with respect to the through-hole can be correctly measured without reference to surface conditions of the work piece and the carrier. By correcting the position of the work piece on the basis of the amount of displacement, the work piece can be positioned with high positioning accuracy.
In the work piece feeding machine, a plurality of the cameras may be located with angular separation of 90xc2x0 and capable of detecting a center of the work piece and a center of the through-hole of the carrier. With this structure, data in the visual field can be efficiently analyzed. The amount of displacement of a center of the work piece with respect to a center of the through-hole in the X-Y directions can be easily measured, so that the work piece can be correctly set in the through-hole.
In the work piece feeding machine, the image processing section may detect the amount of displacement of the work piece with respect to the through-hole on the basis of difference between intensity of direct light, which is emitted from the lighting source section via a gap between the outer edge of the carrier and the inner edge of the through-hole, and intensity of transmitted light, which has transmitted through the work piece and/or the carrier.
In the work piece feeding machine, the lighting source section and the camera respectively may have polarizing filters. By employing the polarizing filters, a direction of a transmission axis (a polarizing axis) can be easily adjusted, so that the amount of displacement of the work piece with respect to the through-hole can be correctly measured by the difference of light intensity.
The abrasive system of the present invention comprises:
an abrasive machine for abrading a work piece;
a sucking mechanism for holding the carrier by vacuum means, the sucking mechanism including a sucking board whose shape is similar to that of the carrier;
a work piece feeding mechanism, which sets a work piece into a through-hole of a carrier and feeds the carrier, which is held by the sucking board;
an accommodating mechanism for accommodating the work piece abraded by the abrasive machine; and
a conveying mechanism for conveying the sucking board to the abrasive machine, the work piece feeding mechanism and the accommodating mechanism.